The industrial robotic system having a workpiece handling robot for manipulating a workpiece and a tool handling robot for manipulating a tool such as a machining tool, a welding torch or a welding gun etc., is generally controlled by a method of teaching playback so as to simultaneously move both the robots in real processing operations.
In the teaching operations for industrial robots before playback operations there are a method of "the sole-acting mode of the manual operation" and a method of "the co-acting mode of the manual operation". The former is adopted for the manipulation of "a position and an attitude of a workpiece" by a workpiece handling robot independently of the manipulation of a tool by a tool handling robot, or for the manipulation of "a position and an attitude of a tool" by a tool handling robot independently of the manipulation of a workpiece by a workpiece handling robot. The latter is adopted for the manipulation of "a position and an attitude of a tool" by a tool handling robot coordinated with an interdependent on the manipulation of "a position and an attitude of a workpiece" by a workpiece handling robot, or for the manipulation of "a position and an attitude of a workpiece" by a workpiece handling robot coordinated with and interdependent on the manipulation of "a position and an attitude of a tool" by a tool handling robot. One of the above mentioned method only is, however, not adopted in the case that many teaching points are required. In such a case, in general, both methods are mutually performed in the middle of teaching operations.
The above mentioned "sole-acting mode of the manual operation" is not explained here because of a prior art. "The co-acting mode of the manual operation" has been created to solve some problems occurred in "the sole-acting mode of the manual operation":
Referring to FIG. 28(a), initially, "a position and an attitude of a workpiece 1m" are manipulated by "a sole-acting mode of the manual operation" of a workpiece handling robot 1 so that an inclination of the tangent of "an aimed point" B.sub.1 regulated on the workpiece 1m comes to a desired inclination .delta..sub.w against the ground 64. And the tip point 57 of a tool is manipulated to "the aimed point" B.sub.1 of the workpiece 1m by "a sole-acting mode of the manual operation" of a tool handling robot 2 so that "a position and an attitude of the tool 2n" comes to a desired inclination .delta..sub.t of "the aimed point" B.sub.1 regulated on the workpiece 1m. From such first state of the workpiece 1m and the tool 2n, teaching points were taught as follows:
The workpiece 1m often contacts or collides with the tool 2n when the workpiece 1m is manipulated by "the sole-acting mode of the manual operation" of the workpiece handling robot 1 as shown by a broken line. In order to avoid such an interference of the workpiece 1m and with tool 2n, the tool 2n positioned at the first state is retired from the workpiece 1m by "the sole-acting mode of the manual operation of the tool handling robot 2 as shown in FIG. 28(b).
And the workpiece 1m is rotated by "the sole-acting mode of the manual operation" of the workpiece handling robot 1 as shown by an arrow 1p in FIG. 28(c), thereby, "a new position and a new attitude of the workpiece 1m" are established so that an inclination of the tangent of "a following aimed point" B.sub.2 regulated on the workpiece 1m comes to the desired inclination .delta..sub.w against the ground 64.
Thereafter, the tip point 57 is returned to "the aimed point" B.sub.2 by "the sole-acting mode of the manual operation" of the tool handling robot 2 as shown in FIG. 28(d) so that the desired inclination .delta..sub.t of "the aimed point" B.sub.2 of the workpiece 1m is achieved by the manipulation of "the position--and the attitude of the tool 2n". The second state of the workpiece 1m and the tool 2n by such above mentioned procedures is taught as "a teaching point" A.sub.2. When "a following teaching point" A.sub.3 is required, the same procedure is performed if the workpiece 1m should avoid the tool 2n. Unless the workpiece 1m interferes with the tool 2n during manipulation of the workpiece 1m, the tool 2n is manipulated to "a following teaching point" A.sub.3 after manipulating the workpiece 1m without retiring the tool 2n from the workpiece 1m.
It is very inconvenient to retire a tool from a workpiece during teaching operations. Many teaching points forces an increase in number of times for retiring the tool from the workpiece. Because, it takes a lot of times to retire the tool and to return the tool, the teaching time is, on the whole, prolonged. Furthermore, an operator often loses sight of "the previous aimed point" on the workpiece when returning the tool to the workpiece. An operator can not often catch "a following aimed point", i.e., "a following teaching point" if the distance between a teaching point and a following one is too short or if the arrangement of a series of teaching points is complicated.
A Japanese unexamined publication No. 61-42004 discloses a robotic system, wherein the manipulation of the tool is subjected to the manipulation of a workpiece in order to solve above mentioned problems. According to the robotic system "a position and an attitude of a workpiece" are manipulated being a tip point of a tool left at a previous teaching point on the workpiece, i.e., the manipulation of "the position and the attitude of the tool" is subjected to that of "the position and the attitude of the workpiece" achieved before the manipulation of the tool so that "a relative position and a relative attitude of the tool against the workpiece" is maintained substantially constant in spite of manipulating "the position and the attitude of the workpiece".
In such a control following the tool up the workpiece, it takes a long time for "a detected position and a detected attitude of the workpiece" to be reflected in the manipulation of "the position and the attitude of the tool". The workpiece often contacts or collides with the tool when the manipulation of "the position and the attitude" of the workpiece is much rapider than that of the tool followed up the workpiece.
In addition, a calculative error of "the position and the attitude of the workpiece" reflects on a calculation of "the position and the attitude of the tool", thereby, the increase of the calculative error of "the position and the attitude of the tool" is promoted. Therefore, the accuracy maintaining "the relative position and the relative attitude of the tool against the workpiece" is remarkably demoted during teaching operations.
A teaching control device for manual operations was proposed in U.S. Pat. No. 5,243,266, wherein "the relative position and the relative attitude of the tool against the workpiece" are maintained by a different control from the above-mentioned manipulation of the tool subjecting to that of the workpiece. In such a control, "a position and an attitude of a workpiece after a preset infinitesimal time interval" and "a position and an attitude of a tool after a preset infinitesimal time interval" are calculated before actually manipulating "a position and an attitude of a workpiece" when receiving "actuating signals" for changing "a position and an attitude of a workpiece". The manipulation of "the position and the attitude of the workpiece" and the manipulation of "the position and the attitude of the tool" are simultaneously and independently controlled by individually manipulating a workpiece handling robot and a tool handling robot based on the above mentioned calculations. An abstract of the control is described as follows:
Referring to FIG. 29(a) initially, "an attitude of a workpiece 1m" is manipulated by "a sole-acting mode of the manual operation" of a workpiece handling robot 1 so that an inclination of the tangent of "an aimed point" B.sub.1 regulated on the workpiece 1m comes to a desired inclination .delta..sub.w against the ground 64. And "a position and an attitude of a tool 2n" is manipulated by "a sole-acting mode of the manual operation" of a tool handling robot 1 so that a tip point 57 of the tool is moved to "an aimed point" B.sub.1 regulated on the workpiece 1m and so that an angle between a tangent B.sub.1s of the aimed point B.sub.1 and the tool 2n comes to .epsilon.. From such first state of the workpiece 1m and the tool 2n, teaching points are taught as below.
The workpiece 1m is rotated in the direction of an arrow 1p by "a co-acting mode of the manual operation" of the workpiece handling robot 1 and the tool handling robot 2 so that an inclination of the tangent B.sub.2s of "a following aimed point" B.sub.2 regulated on the workpiece 1m comes to a desired inclination .delta..sub.w against the ground 64 without changing "a relative position and a relative attitude of the tool 2n against the workpiece 1m" at "the aimed point" B.sub.1.
The tip point 57 of the tool is, then, kept at "the aimed point" B.sub.1 left as shown in FIG. 29(b), and "a position and an attitude of the tool 2n" are manipulated so that an angle between the tangent B.sub.1s of "the aimed point" B.sub.1 and the tool 2n is maintained equal to .epsilon..
Thereafter, as shown in FIG. 29(c), the tip point 57 of the tool is manipulated to "the following aimed point" B.sub.2 regulated on the workpiece 1m by "a sole-acting mode of the manual operation" of the tool handling robot 2. And "the attitude of the tool 2n" is manipulated by "a sole-acting mode of the manual operation" of the tool handling robot 2 so that the angle between the tangent B.sub.2s of "the aimed point" B.sub.2 on the workpiece 2m and the tool 2n comes to .epsilon. as shown in FIG. 29(d). The second state of the workpiece 1m and the tool 2n by such above mentioned procedures are taught as "a teaching point" A.sub.2 of each handling robot, respectively. Incidentally, it is unnecessary to manipulate as FIG. 29(c) if the manipulation from FIG. 29(b) to FIG. 29(d) is directly performable. Naturally, if an angle between the tangent B.sub.2s and the tool 2n is not required .epsilon., any desired different attitude of the tool may be manipulated at the manipulation of FIG. 29(d).
"A following teaching point" A.sub.2 is achieved by the compound procedures of "the co-acting mode of the manual operation" and "the sole-acting mode of the manual operation". If the manipulation of the workpiece 1m is not required, the point A.sub.3 is taught after the manipulation of "the sole-acting mode of the manual operation" of the tool handling robot 2.
The movement of FIG. 29 is substantially different from that of above mentioned FIG. 28, i.e., the workpiece handling robot 1 and the tool handling robot 2 are simultaneously manipulated from FIG. 29(a) to FIG. 29(b). In such "a co-acting mode of the manual operation", the manipulation of "a position and an attitude of the tool 2n" is not subjected to that of "a position and an attitude of the workpiece 1m" but the workpiece handling robot 1 and the tool handling robot 2 are simultaneously and independently manipulated after a preset infinitesimal time interval so that "the relative position and the relative attitude of the tool 2n against the workpiece 1m" is successively maintained constant.
The following matters are comprehensible from the above mentioned description. An operator never loses sight of "the aimed point" B.sub.1 when "the teaching point" A.sub.2 is memorized, since "the relative position and the relative attitude of the tool 2n against the workpiece 1m" is maintained. As the result of keeping the tip point 57 of the tool left at "the aimed point" B.sub.1, an operator easily finds "the teaching point" A.sub.2 on the workpiece 1m when the tip point 57 of the tool is manipulated from "the aimed point" B.sub.1 to "the teaching point" A.sub.2, so teaching operations are rapidly performed.
The following problems are, however, appeared unless "a relative attitude of the tool 2n against the workpiece 1m" is substantially maintained constant. A side of the tool 2n, of which tip point 57 is left at "the aimed point" B.sub.1, often contacts or collides with any protrusion or any wall formed close to "an aimed point" B.sub.1 regulated on the workpiece 1m. But, since "the relative attitude of the tool 2n against the workpiece 1m" is substantially maintained constant as above mentioned, the tool 2n never interferes with the workpiece 1m during the control of "the co-acting mode of the manual operation".
In the welding work, it is very important for an inclination of each point on the welding lines of the workpiece 1m to be constant against the ground. A welding pond 62 is intentionally moved in the direction of the movement of a torch 2n, i.e., in the direction of an arrow 63, if a welding line 61 is inclined downward left as shown in FIG. 30. This inclination .delta..sub.w effects on the depth of welding indicating an essential factor to determine the quality weldment, because, a proper inclination of the welding line 61 promotes the quality of weldment in comparison with a horizontal welding line.
Then, it is desirable to keep "the attitude of the workpiece 1m" so that an inclination .delta..sub.w of the welding line 61 is maintained substantially constant against the ground 64 during the welding work. Naturally, "the attitude of the tool 2n" is determined according to the inclination .delta..sub.w of the welding line 61, therefore, "the attitude of the tool 2n" should also maintained substantially constant against the ground 64 if the inclination of above mentioned welding line 61 is maintained substantially constant against the ground 64.
The welding, of which welding line 61 is inclined downward, is called "a downward slope welding", which has an advantage for a thin workpiece to get a homogeneous weldment because of avoiding an over-welding. On the other hand, in the case of "an upward slope welding", where the welding line is inclined upward along the direction of movement of the torch, a stagnation of welding pond is promoted, therefore, a desired strength of weldment is achieved because of increasing the depth of welding in the thick workpiece.
When the above-mentioned "co-acting mode of the manual operation" is adopted for teaching operations, it is advantageous to cut a procedure of retiring the tool 2n from the workpiece 1m. In such a case, "the relative attitude of the tool 2n against the workpiece 1m" after the manipulation of "the relative attitude of the tool 2n against the workpiece 1m" before the manipulation of "the co-acting mode of the manual operation". But "the relative attitude of the tool 2n against the ground 64" manipulated by "the co-acting mode of the manual operation", i.e., an attitude angle .delta..sub.tb of the tool 2n, is not always same as "the relative attitude of the tool 2n against the ground 64", i.e., an angle .delta..sub.ta, prior to the manipulation of "the co-acting mode of the manual operation", which may be comprehensible by comparing FIG. 29(a) with FIG. 29(b).
The movement of FIG. 29(c) or FIG. 29(d) is, therefore, required in the case that "the relative attitude of the tool 2n against the ground 64" at "the aimed point" B.sub.1 should be same as "the relative attitude of the tool 2n against the ground 64" at "the teaching point" A.sub.2.
As shown in FIG. 29(c), "the position of the tool 2n" are manipulated to "a following aimed point" B.sub.2 regulated on the workpiece 1m by "the sole-acting mode of the manual operation" of the tool handling robot 2. Thereafter, "the attitude of the tool 2n" should be manipulated by "the sole-acting mode of the manual operation" of the tool handling robot 2 so that the inclination .delta..sub.ta of the tool 2n, shown in FIG. 29(a), prior to "the co-acting mode of the manual operation" is achieved without changing "the position of the tool 2n". Such procedures are also inconvenient, especially, many teaching points forces an increase in number of times for manipulating "the attitude of the tool 2n", and besides, it takes a long time for the teaching operations.
The first object of the present invention is to avoid retiring the tool from the workpiece by the co-acting operations of both the robots in order to simplify and to hasten the manual teaching operations.
The second object is to manipulate "the position and the attitude of the workpiece" and the "the position and the attitude of the tool" simultaneously during the execution of the "co-acting mode of the manual operation" without subjecting the manipulation of "the position and the attitude of the tool" to the manipulation of "the position and the attitude of the workpiece", thereby, the change of "the position and the attitude of the tool" and the change of "the position and the attitude of the workpiece" are rapidly performed.
The third object is to prevent the calculation for controlling "the co-acting mode of the manual operation" from integrating calculative errors occurred in the calculation to manipulate the master robot in order to accurately manipulate the workpiece and the tool.
The fourth object is to maintain "the attitude of the tool against the ground" and "the relative position of the tool against the workpiece" substantially constant in the case of manipulating both the robots by "the co-acting mode of the manual operation".
The fifth object is to avoid an undesired downflow of the welding pond and an undesired stagnation thereof according to gravity in the case of the welding work by using a welding torch so that the high quality of weldment is achieved.